1. Field of the Invention
The present invention relates generally to an axial flow fluid compressor and a method of assembling the same.
2. Description of the Related Art
For example, in a rotary compressor, a frame is fixed on the inner wall of a casing, and a main bearing is attached to the frame. The frame is fixed on the inner wall of the casing by means of, e.g. shrinkage fit.
FIGS. 28 and 29 show examples of an axial flow fluid compressor (hereinafter, referred to as "compressor"). The compressor of FIG. 28 is disclosed in U.S. Pat. No. 4,871,304, and that of FIG. 29 is disclosed in U.S. Pat. No. 4,875,842.
As is shown in FIGS. 28 and 29, this type of compressor 111 has a compression section 3 disposed within a sealed casing (hereinafter, called "casing") 2. The compression section 3 comprises a cylinder 7 having both ends opened in its axial direction, and a rotating rod 8 situated eccentrically within the cylinder 7.
Further, a main bearing 15 and a sub bearing 16 hermetically seal the opened ends of the cylinder 7. A main shaft 12 and a sub shaft 13 are inserted into the main bearing 15 and sub bearing 16.
A spiral blade 9 is formed on the peripheral surface of the rotating rod 8. The inside space of the cylinder 7 is divided by the blade 9 into a plurality of working chambers. The working chambers have volumes decreasing gradually from the suction side towards the discharge side.
The cylinder 7 and the rotating body 8 are rotated relative to each other and synchronously by a drive motor 4. The motor 4 comprises a stator 17 fixed on the inner wall of the casing, and a rotor 18 mounted on the cylinder 7 and situated inside the stator 17 so as to be coaxial with the stator 17. A refrigerant gas is compressed by the compression section 3 while it is carried gradually from the suction side to the discharge side of the cylinder 7.
In the compressor 111 of the type wherein the refrigerant gas is compressed while it is carried, if the main bearing 15 is attached to a frame 112, as in the rotary compressor as shown in FIG. 30, an unnecessary space 113 is produced outside the frame 112. As a result, the axial dimension of the casing 2 is increased by the space 113, and the size of the compressor 111 is also increased.
Such an unnecessary space in the casing can be eliminated, if the main bearing 15 is directly fixed on the bottom face of the casing 2 by means of adhesion or welding, as shown in FIGS. 28 and 29. Thus, the increase in size of the compressor 111 can be prevented.
In the compressor 111 shown in FIGS. 28 and 29 wherein the main bearing is directly attached to the casing 2, however, it is difficult to make the axis of the main bearing 15 coincide with the axis of the stator 17 at the time of assembly, though the size of the compressor 111 can be reduced.
In other words, in the compressor 111 shown in FIGS. 28 and 29, it is difficult to keep the squareness of the main bearing 15 in relation to the motor 4. If the axis of the main bearing 15 and stator 17 do not coincide, a motor air gap 19 provided by virtue of a difference between the inside diameter of the stator 17 and the outside diameter of the rotor 18 becomes eccentric. It is thus difficult to keep the entire air gap 19 precisely.
In order to keep the motor air gap 19 at a predetermined value, it is necessary to precisely determine the locations where the main bearing 15 and stator 17 are to be fixed, and the positional relationship between the main bearing 15 and the stator 17.
In addition, it is difficult to fix the main bearing 15 to the casing 2.